Although Apple's other new iPhone models have no such issues, some iPhone 12 mini owners have been complaining of lock screen sensitivity problems that appeared the first time they powered on their handsets. The problem has been reported on both Reddit and the MacRumors forums and Apple still has to come up with an answer.
https://www.notebookcheck.net/Trouble-in-paradise-Apple-iPhone-12-mini-plagued-by-touch-response-issues.504279.0.html